What Is Wilms Tumor?

What Is Wilms Tumor?

Wilms tumor, also referred to as nephroblastoma, is a type of kidney cancer that usually affects children under five years old. Though Wilms tumor is rare, it is the most common form of kidney cancer in children. Wilms tumor usually affects one kidney; rarely, it can affect both kidneys.

Over the years, new advancements have been made in understanding and treating Wilms tumor. Cutting-edge treatments for children with Wilms tumor have significantly improved prognosis.

Stages Of Wilms Tumor


Cancer is categorized into stages to describe where a tumor is located, how large it is, and whether it has spread to other areas of the body. Diagnostic tests are done to obtain this information and assist doctors in recommending the best course of cancer treatment for each child. Different stage descriptions are used for different types of tumors.

A Wilms tumor receives its stage descriptions based on surgery results, analysis of tumor cells, and whether the cancer has spread, as well as where it has spread, if so. Wilms tumor has five stages: Stage I through Stage V. Knowing the stage of cancer helps doctors determine the best course of treatment.

  • Stage I Only one kidney contains a tumor, which can be completely removed by surgery.
  • Stage II Cancer is found in the kidney, soft tissue, fat, and surrounding blood vessels. It may have spread to the renal sinus, the kidney’s entry and exit point for blood and fluid, but has not spread to the lymph nodes. The kidney tumor can be completely removed by surgery.
  • Stage III Cancer has spread beyond the kidney to the nearby organs, blood vessels, abdomen, and lymph nodes but has not spread beyond the abdomen. The cancer cannot be removed completely from the affected kidney with surgery.
  • Stage IV Cancer has metastasized (spread) beyond the original point to distant organs such as the lungs, liver, bones, brain, or lymph nodes outside the abdomen.
  • Stage V – Cancerous tumors are present in both kidneys. In these cases, each tumor is staged separately.

Wilms tumor can also be categorized based on how it responds to treatment: 

  • Refractory Wilms tumor This term is used to describe a Wilms tumor that does not respond to treatment, either during or after treatment.
  • Recurrent Wilms tumor A recurrent Wilms tumor refers to a tumor that returns after treatment. It may appear in the area originally impacted by the cancer or may return elsewhere in the body. In either case, diagnostic tests must be repeated to evaluate the extent of the recurrent cancer.

Signs & Symptoms Of Wilms Tumor


The signs and symptoms of Wilms tumor differ from person to person. Some children do not show any obvious signs. For this reason, it is not uncommon for Wilms tumors to grow large very quickly before they are noticed.

However, most children will experience one or more of the common signs and symptoms of Wilms tumors:

  • A noticeable mass in the abdomen, presenting as a hard lump
  • Swelling and pain in the abdomen

Additional symptoms include:

  • Fever
  • Bloody urine
  • Nausea and vomiting
  • Constipation
  • Loss of appetite
  • Shortness of breath
  • High blood pressure

Wilms tumor is a rare form of cancer, but if you are concerned about any symptoms your child is experiencing, make an appointment with your pediatrician to learn more.

What Causes Wilms Tumor?


Scientific research has not yet uncovered a clear-cut reason for the development of Wilms tumor; however, it is apparent that Wilms tumor often appears in conjunction with certain birth defects and genetic mutations.

Scientists do know that Wilms tumor is caused by DNA changes in the genes of early kidney cells, which affects the healthy development of the kidney. Although children can inherit a gene mutation that can cause Wilms tumor, most gene mutations occur in early childhood, or even during fetal development. Changes in specific genes cause some Wilms tumors, and there are likely other gene changes that have not yet been found. It is not yet known what causes genes to be altered.

Wilms tumor begins in the kidneys of a developing fetus. During the growth of the kidneys, some cells do not mature; they can remain like this even after the child is born, not maturing until the child is about 3 to 4 years old. If these cells do not mature into healthy kidney cells, they can begin to grow out of control, mutating into cancer cells and eventually resulting in Wilms tumor.

Risk Factors

Risk Factors

Researchers have not yet identified any definitive causes of Wilms tumor, although some factors may increase the risk of developing this kind of cancer:

  • Age. Wilms tumor usually affects young children between 3 to 4 years old. Older children and adults rarely develop this condition.
  • Race, ethnicity, and gender. In the United States, the risk of developing Wilms tumor is slightly higher among African Americans and is lowest among Asian Americans. The risk is also slightly higher for biologically female children than it is for biologically male children.
  • Heredity. About one to two percent of children with Wilms tumor have a relative with this type of cancer. In these cases, it is believed that chromosomal damage is inherited from a parent. In addition, the risk of having Wilms tumor in both kidneys is slightly higher for children with a family history. However, most children develop the condition in only one kidney.
  • Abnormalities or other syndromes. Certain birth defects can predispose a child to developing Wilms tumor. These birth defects are sometimes called syndromes. Syndromes include certain symptoms, signs, and other abnormalities that occur at the same time. It is estimated that about one in 10 children with a particular syndrome will also develop Wilms tumor. Examples of such syndromes include:
    • WAGR syndrome. This acronym refers to the physical and mental conditions that occur with this kind of tumor:
      • Wilms tumor
      • Aniridia, a complete or partial lack of iris (color part) in the eye
      • Genitourinary tract abnormalities, including defects of the kidneys, urinary tract, penis, scrotum, clitoris, testicles, or ovaries
      • Range of mental disabilities, including behavioral and psychiatric disorders, and autism spectrum disorder 
    • Denys-Drash syndrome. With this syndrome, the kidneys stop working, eventually causing Wilms tumor to develop in the diseased kidney(s). Additionally, reproductive organs do not develop properly. It is recommended that the diseased kidney(s) be removed if this syndrome develops, as the risk of Wilms tumor is greatly increased
    • Frasier syndrome.  This is similar to Deny-Drash syndrome, except the kidneys may continue to function until adolescence; however, the risk of developing Wilms tumor and cancer of the reproductive organs increases significantly.
    • Beckwith-Wiedemann syndrome. This syndrome is caused by a defective chromosome. It affects children’s growth, making parts of their body larger than normal, including their internal organs, tongue, and possibly arms or legs. Children with this syndrome may also experience other medical difficulties. Children with this condition have a 5 percent chance of having Wilms tumor.
  • Birth defects. Certain birth defects can increase a child’s risk of developing Wilms tumor:
    • Aniridia. This causes a complete or partial absence of the iris (the colored part) in the eye.
    • Hemihypertrophy. This causes people to develop an oversized arm or leg on one side of the body.
    • Cryptorchidism. This prevents the testicles from descending into the scrotum.
    • Hypospadias. This causes the urethra (the urinary opening of the penis) to be located on the underside of the penis.



When left untreated, aortic valve regurgitation can result in complications such as:

  • Heart failure. With aortic valve regurgitation, the heart has to work harder to pump blood around the body. Over time, this weakens the heart, and if left untreated, it can lead to heart failure.
  • Infections of the heart, such as bacterial infections or endocarditis. The likelihood of infection increases with aortic valve regurgitation, especially following valve replacement surgery.
  • Heart arrhythmias. Arrhythmias are irregular or abnormal heart rhythms caused by malfunctioning electrical signals. Aortic valve regurgitation can increase pressure in the heart and weaken the heart over time, increasing the risk of an arrhythmia.
  • Sudden cardiac death. If aortic valve regurgitation is severe and sudden or left untreated for long periods of time, there is a chance of death.



There is no way to prevent aortic valve regurgitation entirely, but certain preventative measures can be taken to reduce the risk. Preventative measures of aortic valve regurgitation include:

  • Maintaining a heart-healthy lifestyle. This includes regular exercise, maintaining a healthy weight, and eating a diet rich in whole grains, lean proteins, fruit, and vegetables. Avoid smoking, foods with high levels of saturated or trans fats, and foods with high salt content.
  • Seeking immediate treatment for strep throat. Strep throat  needs to be treated properly with antibiotics so that it does not progress into rheumatic fever, which can cause aortic valve regurgitation.
  • Checking blood pressure regularly. Make sure your blood pressure stays in a healthy range to help avoid aortic valve regurgitation. If necessary, take medications as prescribed by your doctor to help control your blood pressure.
  • Scheduling regular check-ups with your doctor to monitor heart activity, especially if you have a heart condition or if someone in your family has a valve defect, such as a bicuspid aortic valve. Aortic valve regurgitation or a different heart condition will be easier to treat when diagnosed in its earlier stages.
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